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Unveiling Hidden Neural Codes: SIMPL – A Scalable and Fast Approach for Optimizing Latent Variables and Tuning Curves in Neural Population Data

Dr. Rishabh Pathak
This research paper presents SIMPL (Scalable Iterative Maximization of Population-coded Latents), a novel, computationally efficient algorithm designed to refine the estimation of latent variables and tuning curves from neural population activity. Latent variables in neural data represent essential low-dimensional quantities encoding behavioral or cognitive states, which neuroscientists seek to identify to understand brain computations better. Background and Motivation Traditional approaches commonly assume the observed behavioral variable as the latent neural code. However, this assumption can lead to inaccuracies because neural activity sometimes encodes internal cognitive states differing subtly from observable behavior (e.g., anticipation, mental simulation). Existing latent variable models face challenges such as high computational cost, poor scalability to large datasets, limited expressiveness of tuning models, or difficulties interpreting complex neural network-based functio...
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Continuous Theta Burst Stimulation (cTBS)

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Dr. Rishabh Pathak

Continuous Theta Burst Stimulation (cTBS) is a specific protocol of repetitive transcranial magnetic stimulation (rTMS) that is used to modulate cortical excitability and induce neuroplastic changes in the brain. Here is a detailed explanation of Continuous Theta Burst Stimulation:


1.      Definition:

o   cTBS: Continuous Theta Burst Stimulation is a patterned form of rTMS that involves delivering bursts of magnetic pulses at a specific frequency and intensity over a continuous period of time to a targeted area of the brain. It is characterized by the application of theta-burst patterns of stimulation.

2.     Stimulation Parameters:

o   Theta Burst Pattern: The theta burst pattern consists of bursts of three pulses at 50 Hz repeated at a theta frequency (5 Hz). This pattern is delivered continuously over a specified duration, typically ranging from several seconds to minutes, depending on the research or clinical protocol.

o   Intensity and Duration: The intensity of cTBS is usually set as a percentage of the individual's resting motor threshold, ensuring that the stimulation is tailored to the specific cortical excitability of the target area. The duration of cTBS can vary based on the desired effects and experimental design.

3.     Mechanism of Action:

o   Inhibitory Effect: cTBS is primarily known for its inhibitory effects on cortical excitability. By delivering continuous theta burst patterns, the stimulation leads to a reduction in neuronal firing rates and synaptic transmission in the targeted brain region.

o   Long-Lasting Effects: cTBS has been shown to induce long-lasting changes in cortical excitability, with inhibitory effects persisting beyond the stimulation period. This ability to modulate neural activity and induce plastic changes makes cTBS a valuable tool for studying brain function and potential therapeutic applications.

4.    Applications:

o   Research: cTBS is widely used in research settings to investigate the role of inhibitory mechanisms in cortical function, neural plasticity, and motor learning. Researchers utilize cTBS to study the effects of cortical inhibition on cognitive processes, motor control, and sensory functions.

o Therapeutic Potential: In clinical applications, cTBS is being explored as a potential treatment strategy for neurological and psychiatric disorders. By modulating cortical excitability and neural networks, cTBS may offer therapeutic benefits for conditions such as depression, chronic pain, stroke recovery, and movement disorders.

5.     Clinical Studies:

o  Depression: cTBS has shown promise as a non-invasive treatment for depression, particularly in individuals who are resistant to traditional therapies. By targeting specific brain regions implicated in mood regulation, cTBS may help alleviate depressive symptoms and improve overall well-being.

o  Neurorehabilitation: In the field of neurorehabilitation, cTBS is being investigated as a potential adjunct therapy to enhance motor recovery following stroke, traumatic brain injury, or other neurological conditions. By modulating cortical plasticity, cTBS may facilitate motor relearning and functional recovery.

In summary, Continuous Theta Burst Stimulation is a specialized form of rTMS that exerts inhibitory effects on cortical excitability and induces long-lasting changes in neural activity. With applications in research and clinical settings, cTBS offers insights into brain function, neuroplasticity, and potential therapeutic interventions for a range of neurological and psychiatric disorders.

 

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